Mobility of hindlimb joints in Japanese macaques (Macaca fuscata) as influenced by biarticular musculature.

Joint mobility is a critical issue in the analysis of locomotor adaptation. Here we have attempted precise measurements of the range of extension/flexion of the hip, knee, and ankle joints of Japanese macaques by using fresh cadavers and devising an effective method to fixate the proximal segment. Severance of biarticular muscles revealed restrictions in mobility of as much as 10-25% caused by these muscles. However, incidences of an incomplete removal of the restriction through severance suggest a contribution of cutaneous tissues to the restriction. The mobility ranges determined by this method were compared with the joint motion of Japanese macaques during actual locomotion.